(a) Field of the Invention
The present invention relates to a bright and compact optical-compensation type zoom lens system.
(b) Description of the Prior Art
As for most of optical-compensation type zoom lens systems of medium telephoto class (with focal lengths about 100 mm to 200 mm) which are commercially available at present, the aperture ratios are large and overall lengths of lens systems are also large. Among known optical-compensation type zoom lens systems, there are such lens systems of which the aperture ratios are small and which are designed compactly. However, their qualities of images are not good. Out of known lens systems, the zoom lens system disclosed in the Japanese Published Unexamined Patent Application No. 142,251/78 has a small aperture ratio and favourably corrected aberrations. However, its focal length in the tele-position in not long.